In the field of the acquisition of data transmitted by satellite navigation systems, the technical problem posed is that:                The navigation data are transmitted with the aid of navigation signals whose power is extremely low,        The users have to receive these data in environments which enormously attenuate these signals,        Reception may be interrupted by maskings of the line of sight.        
In order to improve the error rate in the words received (WER for “Word Error Rate”), the data may be encoded as symbols with the aid of various codings (Viterbi, Turbo Code, BCH, Low Density Parity Code [LDPC], etc.). Correct reception of the symbols, and then of the data, is directly related to the energy associated with each symbol.
The known solutions for improving reception are as follows:                Transmit the symbols at a predictable instant and at a predictable location so as to be able to accumulate the energy corresponding to each symbol. This is the solution adopted for sub-frames 1 and 2 of GPS L1C. It is not suited to the transmission of data where the timing of the transmitted data is carried out dynamically, because the data of sub-frames 1 and 2 are transmitted at known times in the course of the frame, thus implying that these data are transmitted implicitly in a synchronous manner, because the frames must be synchronous. This is illustrated by FIG. 1, according to which, for example eight data (“Word 1” . . . “Word 8”, as in the examples of the following figures) are coded, and then transmitted one after the other (“Coded word 1” . . . “Coded word 8”). On reception, after decoding of the successive coded words (in the case of FIG. 1, the decoding of “Coded word 1” must produce “Word 1”), if the receiver has been able to receive sufficient symbols (of “Word 1” in the present case), the corresponding datum is available (“Word 1” rectangle), otherwise, if the receiver has not accumulated enough energy for this datum or if too many symbols have been lost during transmission, the decoding produces a “Nothing” cue.        Increase the energy transmitted per symbol, this not being permitted by the regulations and does not solve the problem of maskings        Increase the duration of a symbol, but this reduces the quantity of symbols that the system can transmit. Moreover, the performance is still limited by the energy associated with each symbol.        Increase the robustness of the coding by increasing the size of this coding. The drawback is the reduction in the bandwidth which is already very limited. Moreover, reception performance is still limited by the energy associated with each message. This is illustrated by FIG. 2 according to which the successive data (“Word 1” . . . “Word 8”) are coded, and then transmitted for example three times each (“Coded word 1”, “Coded word 1”, “Coded word 1”, . . . “Coded word 8”, “Coded word 8”, “Coded word 8”). In a manner analogous to the case of FIG. 1, on reception, the decoding produces as output either the transmitted words if the receiver receives sufficient symbols, or a “Nothing” cue in the converse case.        